This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Certain abbreviations that may be found in the description and/or in the Figures are herewith defined as follows:
ACK acknowledgement
BS base station
COMP coordinated multipoint network operation
CQI channel quality indicator
CRS cell specific reference signal
CRS RSRP cell specific reference signal (CRS) reference signal received power (RSRP)
CSI channel state information
CSI-RS channel state information reference signal
CSI-RS RSRP channel state information reference signal (CSI-RS) reference signal received power (RSRP)
DCI downlink control information
DL downlink
ID identification
eNodeB base station
LPN low power nodes
PBCH physical broadcast channel
PCI Physical Cell Identifier
PDSCH physical downlink shared channel
PDCCH physical downlink control channel
PMI precoding matrix indicator
PSS primary synchronization channel
RI rank indicator
RRH remote radio head
RSRP reference signal received power
RSRQ reference signal received quality
SRS sounding reference signal
SSS secondary synchronization signal
TP transmission point
UE user equipment
UL uplink
VLR visitor location register
VNO visitor location register
Coordinated multipoint (COMP) transmission and reception is one of the technologies investigated in 3GPP LTE-A to enhance specifically the cell-edge data rates in order to create a more uniform data rate experience for the end-user over the entire cell area. These COMP techniques require increased collaboration between different BS nodes (eNodeBs) such as in DL transmission to the UE and UL reception from the UE.
CoMP scenarios for different deployment scenarios are specified in 3GPP Rel. 11. One such CoMP scenario focused on a heterogeneous network which involves the collaboration and/or cooperation within a heterogeneous network, i.e. one or more small cells are placed within the coverage of an eNodeBs. In this CoMP heterogeneous network deployment scenario, denoted as CoMP Scenario 4 in 3GPP, several transmission points (TPs) share the same physical cell-ID. These TPs can include a high-power (macro) transmission point and underlying low-power pico or radio remote heads (RRH) within the coverage area of the high-power transmission point.
In regards to FIG. 1, there is illustrated a 3GPP intra-cell CoMP network scenario. As shown in FIG. 1, there is one macro eNodeB in a coverage area 100 with physical cell identification (PCI) of 100. In this example the macro eNodeB has four TX antennas. Also shown in the coverage area 100 of FIG. 1 are 4 low power network (LPN) devices, such as using eNodeBs or other types of nodes. In FIG. 1 the four LPNs represent four micro-cell type hotspots each have one or more transmit (TX) antennas associated with the macro eNodeB, as well as a respective number of CSI-RS ports configured.
In addition to the macro eNodeB and the underlying LPNs sharing the same physical cell-ID (PCI), they also share the same primary synchronization channel (PSS) and secondary synchronization channel (SSS) as well as a cell specific reference signal (CRS). Consequently they each use all the channels, such as a physical broadcast channel (PBCH) and a physical downlink control channel (PDCCH), which detection and demodulation depends on for the CRS. One might think of only transmitting these channels through the macro eNodeB as the LPNs are supposed to be in the coverage area of the macro, but this would not be a sustainable solution. This is for at least the reason that inter-cell mobility procedures using CRS based mobility measurements, such as CRS reference signal received signal power (RSRP) measurements and/or reference signal received quality (RSRQ) measurements may not be correct. Take for example, a situation where a LPN is close to the cell-border to the neighboring cell having different cell-ID. In this case if the LPN is not transmitting e.g., a CRS signal (common to the serving macro eNodeB) the measured RSRP on the UE side would be based only on the CRS signals from the macro eNodeBs (serving and/or neighbor cells) and would not be able to get full benefit from the improved conditions due to adding the LPN. In general all the TX nodes sharing the same cell-ID are transmitting the same common signals.